The field of the invention relates generally to electric machines, and more particularly, electric machines having air cooling systems.
A number of electric machines include an electric motor. One of many applications for an electric motor is to operate a pump or a blower. The electric motor may be configured to rotate an impeller within a pump or blower, which displaces a fluid. Many gas burning appliances include an electric motor, for example, without limitation, water heaters, boilers, pool heaters, space heaters, furnaces, and radiant heaters. In some examples, the electric motor powers a blower that moves air or a fuel/air mixture through the appliance. In other examples, the electric motor powers a blower that distributes air output from the appliance.
A common motor used in such systems is an alternating current (AC) induction motor. Typically, the AC induction motor is a radial flux motor, where the flux extends radially from the axis of rotation. Another type of motor that may be used in the application described above is an electronically commutated motor (ECM). ECMs include, but are not limited to, brushless direct current (BLDC) motors, permanent magnet alternating current (PMAC) motors, and variable reluctance motors. Typically, these motors provide higher electrical efficiency than an AC induction motor. Some ECMs have an axial flux configuration in which the flux in the air gap extends in a direction parallel to the axis of rotation of the rotor.
A significant problem associated with electric machines is they generate heat, which reduces their efficiency and useful life. Machine components, such as motors and electronic controls, generate high temperatures and are subjected to substantial thermal stresses. Accordingly, efficient cooling systems for the electric machines are necessary to prevent overheating of the components and to improve the overall electrical and mechanical performance and lifetime of the electric machine.
Typically, electric machines require electronic controls for controlling components of the machines, such as user interfaces and motors. Some electric machines have electronic controls coupled to the exterior of motor housings. These externally mounted electronic controls are enclosed to protect them from the environment. However, the enclosures trap heat generated by the electronic controls, reducing the efficiency and useful life of the electronic controls. In addition, heat from the motor is transferred to the electronic controls. Moreover, locating the electronic controls on an end of the motor housing inhibits providing a cooling fan for the motor. Furthermore, current approaches for coupling electronic controls to motor housings are expensive to produce and assemble and are not aesthetically pleasing. Finally, many cooling systems have open fan inlets which expose the electric machine to the environment.